#include <bits/stdc++.h>

using namespace std;
ifstream fin ("litere.in");
ofstream fout ("litere.out");
char a[10001] , b[10001];
int nr , n;
void Interclasare (int st , int  m , int dr)
{
    int k = st;
    int i = st;
    int j = m + 1;
    while (i <= m && j <= dr)
        if (a[i] > a[j])
        {
            b[k++] = a[j++];
            nr += (m - i + 1);
        }
        else b[k++] = a[i++];
    while (i <= m) b[k++] = a[i++];
    while (j <= dr) b[k++] = a[j++];
    for (i = st; i <= dr; i++)
        a[i] = b[i];
}
void MergeSort (int st , int dr)
{
    int m = (st + dr) / 2;
    if (dr - st >= 1)
    {
        MergeSort (st , m);
        MergeSort (m + 1 , dr);
        Interclasare (st , m , dr);
    }
}
int main()
{
    fin >> n;
    for (int i = 1; i <= n; i++)
        fin >> a[i];
    MergeSort (1 , n);
    fout << nr;
    return 0;
}